1. Field of the Invention
The invention relates generally to guidewires, and more particularly, to guidewires for use in accessing small arterial or venous vessels within a patient's body such as the adult radial artery or the arteries of a pediatric patient.
2. Background Information
Recent studies have shown that there are benefits associated with utilizing the radial artery for angiography and other intravascular medical procedures that have typically been performed through the femoral artery. See, for example, Duke Clinical Research Institute article entitled RIVAL Trial Shows Significant Benefits With Radial Approach of Angiography Report dated Apr. 4, 2011. The known procedures for accessing an artery to conduct a medical procedure such as angiography, involves placement of a valved introducer sheath into the artery. The introducer sheath acts as a conduit to pass various medical devices into and out of the artery, while preventing significant blood loss. The introducer sheaths for use with the radial artery approach, which are typically referred to as “micro access” or “micro puncture” sets, accept 5 French (0.066 inch outer diameter) or 6 French (0.079 inch outer diameter) catheters and devices.
The known procedure to place the introducer sheaths into the artery begin with the insertion of a 21-gauge (0.032 inch outer diameter) needle into the artery. A 0.018 inch diameter guidewire is next passed through the needle and into the artery so that the distal portion of the guidewire resides at a desired location within the artery and the proximal portion of the guidewire extends out of the patient. The needle is then withdrawn from the patient over the back of the guidewire, leaving the guidewire extending through the skin and into the artery. Next, a vessel dilator, which is a hollow plastic tube having an outer diameter that is sized to closely fit within the introducer sheath's inner diameter, is placed into the introducer sheath so that the distal end of the dilator extends slightly beyond the distal end of the sheath. The extended distal portion of the dilator has an inner diameter capable of passing over the 0.018 inch guidewire and is smoothly tapered to an outer diameter that is slightly larger than the diameter of the guidewire. The sheath/dilator combination is advanced over the proximal end of the 0.018 inch guidewire and the tapered dilator end is used to gradually enlarge the vessel access site to accommodate the introducer sheath. Once the distal end of the sheath is in place within the vessel, the dilator and the 0.018 inch guidewire are removed from the patient through the inside of the sheath, leaving the valved introducer sheath as an access point for inserting other medical devices.
The 0.018 guidewire is used to support the dilator/sheath combination as that combination is advanced. The amount of force required to allow the dilator/sheath combination to advance tends to bend and kink guidewires of smaller diameters, which prevents the proper insertion of the introducer sheath. The use of a 21-gauge needle is required to accommodate the 0.018 inch guidewire and allow the needle to be withdrawn.
While the insertion procedure works well for access to the relatively large femoral artery, the size of the needle makes it difficult to locate the smaller radial artery. The procedure also makes it difficult to locate either artery in pediatric patients. The difficulty in locating the smaller vessels with the large needles results in the patients being subjected to painful needle sticks followed often by painful movement of the needles.